The ornamental design for a skibootbag, as shown and described.
FIG. 1 is a perspective view of a ski boot bag showing my new design;
FIG. 2 is an inverted bottom rear perspective view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a perspective view thereof in the open position showing the
interior of the ski boot bag, with a ski boot shown therein in dotted line
form as environmental structure only; and
FIG. 5 is a perspective view thereof showing the exterior thereof.